This application is based on application No. JP 2001-169715 filed in Japan, the contents of which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to an image forming method and an image forming apparatus which are improved. More concretely, the present invention relates to a non-fixing type image forming method of forming a toner image on a image receiving sheet and a non-fixing type image forming apparatus to be used for carrying out the image forming method.
2. Description of the Related Art
An image forming method of forming a toner image on an image receiving sheet has been carried out for a long time. The typical method is an electrophotographic image forming method.
In the electrophotographic image formation, an electrostatic latent image carrier such as a photoreceptor is electrified so as to have a predetermined electric potential, and an image is exposed on the charging area according to document image information so that an electrostatic latent image is formed. The electrostatic latent image is developed by using a developer so that a visible toner image is obtained. Further, the visible toner image is finally transferred and fixed onto the image receiving sheet.
Alternatively, there suggest also a direct recording type image forming method of allowing toner to adhere directly to an image receiving sheet based on document image information so as to form and fix a toner image without forming an electrostatic latent image, and a similar method of once forming the toner image directly on an intermediate transfer body so as to transfer and fix the toner image onto the image receiving sheet.
In any methods, according to the conventional image forming methods, a developer which includes toner capable of being fixed onto an image receiving sheet is used. A typical example of the developer is one including hot-melt toner in which pigment or dye is mixed and dispersed in thermoplastic resin.
A toner image composed of such hot-melt toner is finally melt-fixed onto an image receiving sheet made of paper, plastic or the like by heating using a heat roller, infrared or the like. Moreover, at this time, the image receiving sheet is heated under pressure if necessary.
It is difficult to separate the toner fixed onto the image receiving sheet from the image receiving sheet and to reuse the toner and the image receiving sheet. Therefore, when an image receiving sheet onto which a toner image is fixed is unnecessary, it is discarded.
However, as the present public is computerized, a lot of the toner and the image receiving sheets are consumed, so that the energy required for producing them and an amount of exhaust carbon dioxide generated by the production are increasing.
As a method of separating toner from an image receiving sheet in order to reuse an image receiving sheet on which a toner image is fixed, a deinking method utilizing an aqueous solution such as a surface-active agent is also known, but a lot of energy is required to remove moisture impregnating with an image receiving sheet such as paper, and removed toner cannot be reused because it is vitrificated.
Therefore, Japanese Patent Application Laid-Open No. 2000-250249 suggests an image forming method of forming a toner image on an image receiving sheet, more concretely, a non-fixing type image forming method which adopts an image receiving sheet having an uneven surface where a lot of recessed portions are formed capable of housing toner, allows toner to adhere removably to the recessed portions on the uneven surface of the image receiving sheet so as to form a toner image, and protects the toner adhering to the recessed portions by protrusion on the uneven surface of the image receiving sheet so that the adhered toner image is obtained as a formed image, and a non-fixing type image forming apparatus and the like which is suitable for carrying out the image forming method.
This non-fixing type image forming method and the non-fixing type image forming apparatus hold a toner image on an image receiving sheet with the toner image being capable of removed from the image receiving sheet without fixing the toner image thereon like conventional technique so as to capable of forming an image, and separate the toner from the image receiving sheet on which the toner image is formed so as to enable reuse of the toner or (and) the image receiving sheet.
For example, in the non-fixing type image forming method and image forming apparatus suggested in Japanese Patent Application Laid-Open No. 2000-250249, in the case where chargeable toner is used as the toner, the chargeable toner is allowed to removably adhere to the recessed portions of the image receiving sheet by an electrostatic force, so that a toner image can be formed on the image receiving sheet.
However, in such non-fixing type image forming method and image forming apparatus, when the chargeable toner is allowed to adhere to the recessed portions on the uneven surface of the image receiving sheet by the electrostatic force so that the toner image is formed on the image receiving sheet, if the surface of the sheet is allowed to approach an electrostatically charged object (for example, electrostatically charged sheet or the like), the toner on the image receiving sheet is attracted to the electrostatically charged object so as to be occasionally peeled from the image receiving sheet. For example, when the image receiving sheet on which the toner image is formed is overlapped with another electrostatically charged image receiving sheet or the image receiving sheet on which the toner image is formed is filed in an electrostatically charged file, the toner is occasionally peeled from the toner image on the image receiving sheet.
The present invention is made in view of these circumstances, and the object is to provide improved image forming method and image forming apparatus. More specifically, the object is to provide improved non-fixing type image forming method and image forming apparatus.
More concretely, it is an object of the present invention to provide a non-fixing type image forming method of forming a toner image on an image receiving sheet, which holds the toner image onto the image receiving sheet removably without fixing the image like conventional techniques to be capable of forming the image, and thus separates and removes the toner from the image receiving sheet on which the toner image is formed to enable reusing of the toner or (and) the image receiving sheet, and is capable of forming the toner image remaining stably on the image receiving sheet onto the image receiving sheet with a damage of the image due to an object having electric charges (for example, a sheet having electric charges) which occasionally approaches from an outside being suppressed. Further, it is an object of the present invention to provide a non-fixing type image forming apparatus which is suitable for carrying out the non-fixing type image forming method.
In order to achieve the above and another objects, the image forming method according to a certain aspect of the present invention is a non-fixing type image forming method of forming a toner image on an image receiving sheet, which adopts an image receiving sheet having an uneven surface formed with a lot of recessed portions capable of housing chargeable toner as the image receiving sheet, and allows the chargeable toner to removably adhere to the recessed portions on the uneven surface of the image receiving sheet by means of an electrostatic force to form a toner image, and allows protrusions on the uneven surface of the image receiving sheet to protect the toner adhering to the recessed portions. In this method, after the toner image is formed on the image receiving sheet, an amount of electric charges of the toner on the image receiving sheet is reduced.
Further, in the image forming method, after the toner image is formed on the image receiving sheet, a surface potential of the image receiving sheet is reduced to not more than 100 V with absolute value.
In addition, the image forming apparatus according to a certain aspect of the present invention is a non-fixing type image forming apparatus which has a toner image forming apparatus for allowing chargeable toner to removably adhere to recessed portions of an image receiving sheet having an uneven surface formed with a lot of recessed portions capable of housing the chargeable toner by means of an electrostatic force to form a toner image on the image receiving sheet. In this image forming apparatus, an electric charge reducing apparatus for reducing an amount of electric charges of the toner on the image receiving sheet after forming the toner image is provided on a downstream side in an image receiving sheet carrying direction with respect to a toner image forming area on the image receiving sheet by the toner image forming apparatus.
Preferably in the image forming apparatus, a protrusion toner removal apparatus for removing the toner adhering to top portions of protrusions on the uneven surface of the image receiving sheet is provided on the downstream side in the image receiving sheet carrying direction with respect to the toner image forming area on the image receiving sheet by the toner image forming apparatus. The electric charge reducing apparatus is provided on the downstream side in the image receiving sheet carrying direction with respect to the toner image forming area and on an upstream side with respect to the protrusion toner removal apparatus or (and) a downstream side with respect to the protrusion toner removal apparatus.
Further, the electric charge reducing apparatus includes an electrically conductive sheet which is brought into contact with a surface of the image receiving sheet on which the toner image has been formed.
In another aspect, the electric charge reducing apparatus includes an electrically conductive roller which is brought into contact with the surface of the image receiving sheet on which the toner image has been formed.
In still another aspect, the electric charge reducing apparatus is an ion generating apparatus which strews ions over the surface of the image receiving sheet on which the toner image has been formed by means of ion flow.
In still another aspect, the electric charge reducing apparatus includes a charger which faces the surface of the image receiving sheet on which the toner image has been formed.
Furthermore, the electric charge reducing apparatus reduces the surface potential of the image receiving sheet where the toner image has been formed to not more than 100 V with absolute value.